Many people have sought for a long time to modify the colour of their hair and in particular to mask their grey hair.
It is known practice to obtain “permanent” or oxidation dyeing with dye compositions containing oxidation dye precursors, which are generally known as oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidation bases are initially colourless or weakly coloured compounds, which, when combined with oxidizing products, may give rise to coloured compounds via a process of oxidative condensation.
The variety of molecules used as oxidation bases and couplers allows a wide range of colours to be obtained.
It is also known practice to dye keratin fibres temporarily with direct dyes, which are coloured and colouring molecules that have affinity for the fibres. The direct dyes generally used are chosen from nitrobenzene, anthraquinone, nitropyridine, azo, methine, azomethine, xanthene, acridine, azine and triarylmethane direct dyes. The presence of such compounds enables the colouring obtained to be further enriched with tints or enables the chromaticity of the colouring obtained to be increased. This direct dyeing may be performed at acidic, neutral or alkaline pH and in the presence or absence of an oxidizing agent.
Dyeing, whether direct dyeing or oxidation dyeing, must moreover satisfy a certain number of requirements. Thus, it must be free of toxicological drawbacks, it must enable the desired shades to be obtained and it must show good resistance to external attacking factors such as light, bad weather, washing, permanent waving, perspiration and rubbing.
The dyeing process must also make it possible to obtain shades that are as unselective as possible, i.e. it must produce the smallest possible colour differences all along the same keratin fibre, which generally comprises areas that are differently sensitized (i.e. damaged) from its end to its root.
The compositions used in the dyeing process must also have good mixing and application properties on keratin fibres, and in particular good rheological properties so as not to run, when they are applied, onto the face, onto the scalp or beyond the areas that it is proposed to dye.
Direct dyeing is usually performed in a lightening dyeing process using at least one dye composition comprising a direct dye and at least one oxidizing composition, which are mixed together at the time of use just before application to the fibres. Specifically, it is not possible to store in the same composition all the ingredients except the water, so as to avoid degradation of the hydrogen peroxide in alkaline or neutral aqueous medium, and denaturation of the direct dyes by prolonged contact in oxidizing medium and consequently a reduction of the dyeing power of the said dyes on the keratin fibres.
Thus, according to the usual practice, the dye composition(s), on the one hand, and the oxidizing aqueous composition, on the other hand, which has an acidic pH to ensure the stability of the hydrogen peroxide, are stored separately, and are not placed in contact until the time of use.
The need to use several compositions first entails drawbacks inherent in the storage of several compositions, with a larger storage area.
This moreover entails the need to measure out the compositions before placing them in contact. To overcome this drawback, it may be proposed to use kits (or multi-compartment devices), but this nevertheless complicates the use of the compositions and increases the costs. Furthermore, in certain cases, the dye compositions and oxidizing compositions are in different galenical forms, for instance powders, granules, pastes or creams, which may complicate the mixing and the production of a homogeneous final composition (see, for example, US 2007/0006, US 2008/0 263 786, US 2009/0 056 039, US 2010/064 449, EP 23601604, WO 2012/015 034, WO 11/059 027, US 2011/203 604, FR 0 756 173 and EP 2 011 474). In addition, it is seen that the compositions derived from these powders, granules, pastes and creams do not always give compositions with textures that are easy to apply. Furthermore, the mixtures obtained do not always give the keratin fibres satisfactory colours, especially in terms of intensity, dyeing power, chromaticity and/or sparingly selective colourings, i.e. colourings that are sparingly homogeneous between the root and the end of the fibre. Moreover, they do not always lead to easy application with a suitable consistency.
Furthermore, during the use of pulverulent dye compositions, there may be a risk of the user coming into contact with the dyes and the alkaline agents.